Pretreatment: making good black mass
Black mass quality decides refining cost. Cells are discharged, then shredded in a controlled atmosphere to manage fire risk. Magnetic separation removes steel, eddy-current separation removes aluminium, and air classification and screening separate foils and plastics from the fine active material.
Electrolyte and binder must also be dealt with. Thermal or other pretreatment removes organic solvents and breaks down binders, while capturing fluorine compounds so they are not released. Well-prepared black mass leaches faster and needs fewer purification steps.
- Controlled discharge before any mechanical work
- Shredding under controlled atmosphere
- Separation of steel, aluminium, copper and plastics
- Capture of electrolyte and fluorine compounds
Leaching, separation and product quality
Black mass is leached in acid, typically with a reducing agent, to dissolve lithium, nickel, cobalt and manganese. Impurities such as iron, aluminium and copper are removed by precipitation, and graphite is filtered out as a separate residue. Solvent extraction then separates the metals into individual solutions.
Crystallisation and precipitation turn those solutions into saleable products. Each batch is assayed against battery-grade specifications before release, because trace impurities at parts-per-million levels can affect cathode performance.
| Product | Recovered as | Main use |
|---|---|---|
| Lithium | Carbonate or hydroxide | Cathode production |
| Nickel | Nickel sulphate | Precursor for nickel-rich cathodes |
| Cobalt | Cobalt sulphate | Precursor for NMC and NCA cathodes |
| Manganese | Manganese sulphate | Precursor for NMC and LMO cathodes |
| Graphite | Filter residue | Further treatment or other uses |
Field note